Data Analysis Interview Questions

1. What is the difference between Primary Key and Foreign Key? (SQL Basics)
2. Write a query to find the second highest salary in the Employee table.
3. How do you handle missing values in a dataset? (Data Cleaning)
4. What is the difference between COUNT(*), COUNT(column), and COUNT(DISTINCT column)?
5. What are measures of central tendency in statistics? (Stats Basics)
6. What is a window function in SQL? Provide examples of ROW_NUMBER and RANK.
7. Write a query to fetch the top 3 performing products based on sales.
8. Explain the difference between UNION and UNION ALL.
9. Explain p-value in hypothesis testing. (Statistics)
10. How would you detect outliers in a dataset? (EDA)
11. Write a query to get the top 3 departments with the highest average salary. (SQL + Aggregation)
12. What is correlation? How do you interpret it? (Statistics)
13. Explain the difference between DELETE and TRUNCATE commands.
14. What are KPIs? Give examples for an e-commerce company. (Business)
15. How do you calculate a running total in SQL? (Window Functions – Advanced SQL)
16. Explain the difference between Correlation and Regression. (Stats)
17. How do you handle imbalanced datasets in classification problems? (ML + Analytics)
18. How would you design an A/B test for a new pricing model? (Experiment Design)
19. How would you detect anomalies in financial transactions? (Real-World Case)


Data Analysis/Scenario-Based Questions

20. Write a query to identify the most profitable regions based on transaction data.
21. How would you analyze customer churn using SQL?
22. Explain the difference between OLAP and OLTP databases.
23. How would you determine the Average Revenue Per User (ARPU) from transaction data?
24. Describe a scenario where you would use a LEFT JOIN instead of an INNER JOIN.
25. Write a query to calculate YoY (Year-over-Year) growth for a set of transactions.
26. How would you implement fraud detection using transactional data?
27. Write a query to find customers who have used more than 2 credit cards for transactions in a given month.
28. How would you approach a business problem where you need to analyze the spending patterns of premium customers?